如何在不使用数组的情况下读取字符串并存储到不同的变量中

Question

我有一个家庭作业，我应该以这种格式读取一个字符串 [1+2/3+4] 然后我必须存储 5 个变量，它们是前 3 个数字和前 2 个运算符。我的问题是如何遍历字符串并将值存储到不同的变量中。这就是我目前所拥有的。

公共类表达式评估{

static String expression;
static double o1;
static double o2;
private static double o3;
static char operator1;
private static char operator2;

public static  String getOperand(String s) {
    s = s.trim();
    String num = "";



    while (s.length() > 0 && s.charAt(0) >= '0' && s.charAt(0) <= '9') {



     num = num + s.charAt(0);
     s = s.substring(1);

    }

    expression = s;
    return (num);
}

public static char getOperator(String s) {
    s = s.trim();
    char r = 0;
    int i = 0;
    while (s.length() > 0 && s.charAt(0) >= '0' && s.charAt(0) <= '9') {

        r = s.charAt(i);
        s = s.substring(i+1);

        i++;
    }



    return (r);
}


public static double add(double a, double b) {

    return (a + b);

}

public static double sub(double a, double b) {

    return (a - b);

}

public static double mult(double a, double b) {

    return (a * b);

}

public static double div(double a, double b) {

    return (a / b);

}

public static double solveExpresion(String e) {

    double answer = 0;

    for(int i = 0;i< e.length();i++){

    String operand1;
    String operand2;

    operand1 = getOperand(e);
    o1 = Double.parseDouble(operand1);

    operand2 = getOperand(expression);
    o2 = Double.parseDouble(operand2);

    operator1 = getOperator(expression);





    }

    return (answer);


}
}

这是我的主要课程

    import java.util.Scanner;

    public class TestCalc {

public static void main(String args[]) {

    Scanner kb = new Scanner(System.in);

    String equation;
    System.out.println("Please enter your equation: ");
    equation = kb.nextLine();

    double newNum = ExpresionEvaluation.solveExpresion(equation);

    //System.out.println(newNum);

    System.out.println(ExpresionEvaluation.o1);
    System.out.println(ExpresionEvaluation.operator1);
    System.out.println(ExpresionEvaluation.o2);
    //System.out.println(ExpresionEvaluation.expression);
}

}

每次我运行它都说我有一个空字符串。

Answer 1

这是我按预期检索 5 个变量的快速解决方案，使用 Matcher/Pattern：

    public static void main(String[] args) throws ParseException {
        String operation = getOperationFromInput();
        List<Integer> firstThreeNumbers = retrieveFirstThreeNumbers(operation);
        List<Character> firstTwoOperators = retrieveFirstTwoOperators(operation);
        printNumbersAndOperators(firstThreeNumbers, firstTwoOperators);
    }

    private static String getOperationFromInput() {
        Scanner scanner = new Scanner(System.in);
        scanner.useDelimiter("\n");
        return scanner.next();
    }

    private static List<Integer> retrieveFirstThreeNumbers(String operation) {
        List<Integer> firstThreeNumbers = new ArrayList<>();
        Pattern patternNumber = Pattern.compile("\\d");
        Matcher matcher = patternNumber.matcher(operation);
        for (int i = 0; i < 3 && matcher.find(); i++) {
            firstThreeNumbers.add(Integer.valueOf(matcher.group()));
        }
        return firstThreeNumbers;
    }

    private static List<Character> retrieveFirstTwoOperators(String operation) {
        List<Character> firstTwoOperators = new ArrayList<>();
        Pattern patternOperator = Pattern.compile("[+-/*]");
        Matcher matcher = patternOperator.matcher(operation);
        for (int i = 0; i < 2 && matcher.find(); i++) {
            firstTwoOperators.add(matcher.group().charAt(0));
        }
        return firstTwoOperators;
    }

    private static void printNumbersAndOperators(List<Integer> firstThreeNumbers, List<Character> firstTwoOperators) {
        System.out.println(firstThreeNumbers + " " + firstTwoOperators);
    }

在这段代码中，我将前三个数字存储在 List<Integer> 中，前两个运算符存储在 List<Character> 中。

有多种方法可以实现一个解决方案，所以作为一个家庭作业，尝试找到其他方法:)